The invention relates to a method for communication in a radio communications system in which the base station uses different transmission directions successively in order to transmit messages to subscriber stations. The invention also relates to a base station and to a subscriber station for carrying out the method.
In radio communications systems, messages, for example with speech information, image information, video information, SMS (Short Message Service), MMS (Multimedia Messaging Service) or other data are transmitted by electromagnetic waves via a radio interface between a transmitting and a receiving station. In this case, depending on the specific configuration of the radio communications system, the stations may be different types of subscriber-end radio stations or network-end base stations. At least some of the subscriber stations in a mobile radio communications system are mobile radio stations. The electromagnetic waves are transmitted at carrier frequencies which are in the frequency band provided for the respective system.
Mobile radio communications systems are often in the form of cellular systems, for example in accordance with the GSM (Global System for Mobile Communication) or UMTS (Universal Mobile Telecommunications System) Standard with a network infrastructure comprising, for example, base stations, facilities for monitoring and control of the base stations, and further network-end facilities. In addition to these cellular, hierarchical radio networks, which are organized to cover large areas (supralocal), wire-free local area networks (WLANs, Wireless Local Area Networks) also exist, whose radio coverage area is generally spatially considerably more confined.
Examples of different Standards for WLANs are HiperLAN, DECT, IEEE 802.11, Bluetooth and WATM.
In radio communications systems, multiple access methods/multiplexing methods (Multiple Access, MA) are used to control the access by subscriber stations to the common transmission medium. In these multiple access methods, the transmission medium can be split in the time domain (Time Division Multiple Access, TDMA), in the frequency domain (Frequency Division Multiple Access, FDMA), in the code domain (Code Division Multiple Access, CDMA) or in the space domain (Space Division Multiple Access, SDMA) between the subscriber stations. Combinations of multiple access methods are also possible, for example the combination of a frequency domain multiple access method with a code domain multiple access method.
When using space domain multiple access methods, a base station can transmit information directionally in specific transmission directions to one subscriber station. During this process, it is possible for the beam to follow the movement of the subscriber station, or for discrete transmission directions to be used, between which switching takes place during movement of the subscriber station. Alternatively, in the case of methods which are known by the expression beam hopping, the base station uses the random principle to select one transmission direction and to transmit messages to subscriber stations in the area covered by the respective transmission direction.